A neighbor ran into their bedroom and in that split second it was clear -- their house was on fire.

They ran down the stairs of the stilted Ramrod Key home as the flames were leaping skyward.

"Didn't have time to really grab anything," Jack Sauder said Monday, just hours after the fire. "Lisa grabbed JJ and we all made it out OK, but nothing else made it."

Across the street, Ed and Gale Upmal met the Sauders and watched as the home at 27383 Anguilla Lane burned in a blue-flamed roar.

"I've seen a few fires, but nothing like this," Ed Upmal said. "The wind was coming from the north and was blowing the flames through the windows -- these blue, square, roaring flames. And there was more than one explosion."

There were no reported injuries in the fire that started around 1:13 a.m.

The fire was so intense it could be seen three miles away as firefighters traveled from Marathon and Big Coppitt Key. Fire trucks raced along U.S. 1 knowing they would find at least one structure and maybe more engulfed, said Monroe County Fire Rescue Chief Jim Callahan.

"The guys [firefighters] crossing the bridge on Big Pine [Key], just said, 'Oh, God,'" Callahan said. "It was clear to everyone it was going to be a big one."

A neighbor, only identified as Jeff -- whose last name could not be confirmed Monday -- first beat on the Sauders' front door, Callahan said. The flames grew fast and finally he ran into the house and woke the Sauders.

All three were able to make it out safely. By chance, the Sauders went to sleep without locking their front door.

"Thank God for that neighbor," Callahan said, adding that the smoke alarm inside the house wasn't working. "We would absolutely have two fatalities if he hadn't been there."

Investigators believe the fire was likely caused by the 37-foot, fiberglass RV parked next to the house. The RV did have a working smoke alarm and that was what reportedly woke the neighbor who had his windows open due to the cooler weather, Callahan said.

The RV also housed a large propane tank that could have accelerated the blaze, the fire chief said.

The flames quickly jumped to the house and two heavy-duty equipment trailers -- one that stored welding tanks and gear and one that contained two Harley-Davidson motorcycles, Callahan said.

Because of the intensity of the fire, nearby neighbors were evacuated.

Jack Sauder operates a boat cover and awning business and Lisa is a welder who builds tuna towers for off-shore fishing boats, Jack Sauder said. Most of their equipment was lost, he said.

The fire engulfed all four structures and then turned toward the canal and a 25-foot World Cat boat with twin outboard engines, which was also lost in the blaze. The boat burned to the water line.

The only structure remaining Monday afternoon was the metal roof of the house as most of the walls had collapsed. Flames still flickered on some timbers.

The fire took about an hour to bring under control and crews remained on scene until 7 a.m., Callahan said.

The fire chief estimates the damage to be more than $500,000. That could increase after the state fire marshal concludes its investigation, which is ongoing.

The Monroe County Property Appraiser lists the home and property to be worth $237,685 as of this year's assessment.

Jack Sauder said he was still working with insurance adjusters Monday afternoon. The house was insured, but none of the motorcycles, RV or equipment was insured, Jack Sauder said.

The fire melted the plastic siding on the neighbor's home who awoke the Sauders, but didn't appear to damage the home structurally, Callahan said.

The American Red Cross is providing the Sauders with food, clothing and lodging.

"We'll provide that until we figure out what is needed next," said J.B. Hunt, of the Red Cross. "They lost everything in the fire."